A chromosomal region 7p11.2 transcript map: Its development and application to the study of EGFR amplicons in glioblastoma

Abstract

A P R I L 2 0 0 2 Neuro-Oncology Cumulative information available about the organization of ampliied chromosomal regions in human tumors suggests that the ampliication repeat units, or amplicons, can be of a simple or complex nature. For the former, ampliied regions generally retain their native chromoso-mal connguration and involve a single ampliication target sequence. For complex amplicons, ampliied DNAs usually undergo substantial reorganization relative to the normal chromosomal regions from which they evolve, and the regions subject to ampliication may contain multiple target sequences. Previous efforts to characterize the 7p11.2 epidermal growth factor receptor (EGFR) ampli-con in glioblastoma have relied primarily on the use of markers positioned by linkage analysis and/or radiation hybrid mapping, both of which are known to have the potential for being inaccurate when attempting to order loci over relatively short (< 1 Mb) chromosomal regions. Due to the limited resolution of genetic maps that have been established through the use of these approaches, we have constructed a 2-Mb bacterial and P1-derived artii-cial chromosome (BAC-PAC) contig for the EGFR region 3 Abbreviations used are as follows: BAC, bacterial artiicial chromosome; EGFR, epidermal growth factor receptor; EST, expressed sequence tag; ORF, open reading frame; PAC, P1-derived artiicial chromosome; PCR, polymerase chain reaction; RT, reverse transcriptase; STS, sequence tagged site. and have applied markers positioned on its associated physical map to the analysis of 7p11.2 ampliications in a series of glioblastomas. Our data indicate that EGFR is the sole ampliication target within the mapped region, although there are several additional 7p11.2 genes that can be coampliied and overexpressed with EGFR. Furthermore , these results are consistent with EGFR ampli-cons retaining the same organization as the native chromosome 7p11.2 region from which they are derived.